The present invention relates to screw drivers and more particularly to an adapter for prompt engagement a shank of screw driver with a handle into which the shank of the screw driver is readily engaged.
A prior art adapter 10 (as shown FIGS. 1, 2 and 3) which has a rear end connected to a handle (not shown), a polygonal central bore 101 in the front end, a concaved outer periphery 11 wrapped with a spring 12, a plurality of conical through holes 13 spacedly formed around a central portion of the concaved periphery for respectively disposing a plurality steel ball 14 therein, an annular sleeve 15 slidably sleeved on the concaved outer periphery 11 having an annular convex 17 biased by the spring 12 including a sloped upper surface and a receiving space 16 above the sloped upper surface to receiving the steel balls 14 when they move outward. A polygonal shank 1 of a screw driver has a plurality of the semi-circular grooves 3 spacedly formed around a middle periphery respectively engageable with the steel balls 14. The annular convex 17 is normally stopped against the steel ball 14 to prevent them from moving outward (as shown in FIG. 1). When the shank 1 inserts into the central bore 101. The user has to grip the hand with one hand and use the fingers of that hand to pull the sleeve 15 rearward to permit the steel balls 14 moving into the receiving space 16 and uses the other hand to insert the shank 1 into the central bore 101 of the adapter 10. So that the shank 1 can be able to freely slide in the central bore 101 (as shown in FIG. 2). When the shank 1 is inserted in place into the central bore 101, the user can release the sleeve 15 and the annular convex 17 biased by the spring 12 moves upward to force the steel balls 14 moving inside to respectively engaged within the semi-circular grooves 3 of the shank 1 (as shown in FIG. 3). This type of adapter 10 gives great inconvenience to user because the user has to use one hand to the synchronously perform two actions.
Another adapter (as shown in FIGS. 4 and 5) is of a pneumatically tool adapter 60 which has a hollow interior tubular body, a stepped outer periphery, an annular sleeve 61 wrapped on the front portion of the tubular body biased by a first spring 62, a resistant member 63 inside the central bore of the tubular body biased by a second spring 64 and having plurality of air vents 631 spacedly formed in the bottom, a steel ring 632, an annular cushion 633 and a steel ring 634 under the air vents 631, a cylinder wall 635 and a press ring on the top of the resistant member 63, a plurality of steel balls 65 spacedly disposed in side a plurality of through holes in the peripheral wall of the tubular body and mutually stopped by the cylinder wall 635 and the sleeve 61 and an air pipe 66 connected to the rear end of the tubular body for supplying the high pressure air into the tubular body, in use, don't have to move the sleeve 61 but just insert the lower end of a air pipe 67 of a pneumatic tool into the central bore of the tubular body to press the resistant member downward until the annular groove 671 of the air pipe reached to the steel balls 65 which are pressed by the sleeve 61 will automatically engage into the annular groove 671 therefore to arrest the air pipe 67. This arrangement is very skillfully and convenient, but don't suitable to engage a shank of a screwdriver.
Still another prior art adapter 70 (as shown in FIG. 6) comprises a hollow interior tubular body having a central bore 71, an annular sleeve 72 slidably wrapped on the concaved outer periphery of the tubular body, a plurality of conical through holes 74 spacedly formed in the concaved outer periphery for respectively disposed a plurality of steel balls 75 therein, a roughly inverse U-shaped cap 76 slidably disposed into the central bore 71 having a pair of transverse ends 761 stopped against a pair of shoulders 701 in the central bore 71, a spring 77 biased the inverse U-shaped cap 76 having a lower end stopped against the top of an inverse U-shaped bottom 78, which is connected to the inner periphery of the tubular body by punching. In use, directly insert a shank of a screw driver into the central bore 71 to press the inverse U-shaped cap 76 moving downward. When the groove of the shank reaches to the still balls 75 they will automatically engaged into the groove of the shank under the pressure of the sleeve 72. The shank of the screw driver is therefore fixed in the central bore 71. This type of adapter is more convenient than the others. However, it has at least the following disadvantages:                a) the resilient force of the spring 77 is too strong, when inserts the shank into the central bore 71, it may be rebound out to hurt people,        b) it requires more parts, the assembly of the parts is complicated and cost more,        c) the inverse U-shaped member 78 is not integrated with the tubular body but is punched to connect the tubular body, so the torque is therefore weak,        d) the lower end of the spring 77 is freely disposed on the top of the inverse U-shaped member 78, it may be inclined toward one side and deformed that affect its resilient force, and        e) the central bore 71 has an enlarged bottom that affect its intensity.        